The present invention is directed systems, apparatus and methods for the storage of information.
Magnetic storage has a limited storage lifetime, bit density, and volatility. The magnetic medium used in traditional disk storage degrades within a decade. The information is stored in small magnetic bit regions through magnetizing each region in a particular direction. Over time, the magnetization of the bit regions is corrupted by external electromagnetic forces or through exposure to the Earth's magnetic field or by thermal upsets. Thermal upsets are statistical processes that occur when the magnetization of a bit is thermally activated to overcome the anisotropy barrier. Magnetic tape is used extensively for archiving, but the tape deteriorates over time. With magnetic tape, there is an additional cost associated with controlling the temperature and humidity in order to slow down the deterioration of the tape. Another disadvantage of magnetic tape is that the access time for getting information from a particular part of the tape is long.
As electronic recording evolves and more information is digitized, there exists not just a critical necessity for storage volume but also increased storage permanency. A need exists for high density, stable, non-volatile memory with a longer storage life and less potential to be corrupted by external influences.
FIG. 1 is a schematic diagram of a prior art reader and writer. Information may be erased by exposure to a magnetic field or radiation. Information density/lifetime is limited by the superparmagnetic limit. Storing information for seven years requires KuV/kBT>50 where Ku=crystalline anisotropy per unit volume, V=bit volume, kB=Boltzman constant, and T=absolute temperature. Notably, there is a trade-off between high density and retention time.